Certain embodiments of the present invention generally relate to an electrical connector assembly mating interface in which L-shaped ground shields isolate differential contact pairs from one another.
It is common, in the electronics industry, to use right angled connectors for electrical connection between two printed circuit boards or between a printed circuit board and conducting wires. The right angled connector typically has a large plurality of pin receiving terminals and, at right angles thereto, pins (for example compliant pins) that make electrical contact with a printed circuit board. Post headers on another printed circuit board or a post header connector can thus be plugged into the pin receiving terminals making electrical contact there between. The transmission frequency of electrical signals through these connectors may be very high and require, not only balanced impedance of the various contacts within the terminal modules to reduce signal lag and reflection, but also shielding between rows of terminals to reduce crosstalk.
Impedance matching of terminal contacts has already been discussed in U.S. Pat. Nos. 5,066,236 and 5,496,183. Right angle connectors have also been discussed in these patents, specifically how the modular design makes it easier to produce shorter or longer connectors without redesigning and re-tooling for an entirely new connector, and only producing a new housing part into which a plurality of identical terminal modules are assembled. As shown in the '236 patent, shielding members can be interposed between adjacent terminal modules. An insert may be used to replace the shield or a thicker terminal module may be used to take up the interposed shielding gap if the shielding is not required. The shield disclosed in the '236 patent is relatively expensive to manufacture and assemble. The shielded module disclosed in the '183 patent includes a plate-like shield secured to the module and has a spring arm in the plate section for electrically engaging an intermediate portion of a contact substantially encapsulated in a dielectric material. The shield arrangement of the '183 patent, however, requires sufficient space between adjacent through-holes of the board to avoid inadvertent short circuits. Furthermore, both the insulated module and the shield must be modified if the ground contact is to be relocated in the connector.
An alternative electrical connector assembly has been proposed in U.S. Pat. No. 5,664,968, in which each terminal module has a plurality of contacts including a mating contact portion, a connector portion and an intermediate portion there between with some or all of the intermediate portion encapsulated in an insulated web. Each module has an electrically conductive shield mounted thereto. Each shield includes at least a first resilient arm in electrical engagement with a selected one of the contacts in the module to which the shield is mounted and at least a second resilient arm extending outwardly from the module and adapted for electrical engagement with another selected contact in an adjacent terminal module of the connector assembly.
An alternative connector apparatus has been disclosed in U.S. Pat. No. 6,231,391. The '391 patent describes a header connector including a header body, a plurality of signal pins, a continuous strip having a plurality of shield blades formed thereon, and a plurality of ground pins. The header body includes a front wall having a plurality of signal pin-receiving openings, a plurality of shield blade-receiving openings, and a plurality of ground pin-receiving openings. The shield blade-receiving openings are formed to have a generally right angle cross-section. A plurality of shield blades are also formed with a generally right angle cross-section and are located adjacent to individual signal pins such that each signal pin is provided with a corresponding ground shield.
Conventional connector assemblies, such as in the '236, '183, '968 and '391 patents, are designed for use both in at least single-ended applications and may also be used in differential pair applications. In single-ended applications, the entire signal content is sent in one direction contained between ground and one conductor and then the entire signal content is subsequently returned in the opposite direction contained between ground and a different conductor. Each conductor is connected to a pin or contact within a connector assembly, and thus the entire signal content is directed in one direction through one pin or contact and in the opposite direction through a separate pin or contact. In differential applications, the signal is divided and transmitted in the first direction over a pair of conductors (and hence through a pair of pins or contacts). The return signal is similarly divided and transmitted in the opposite direction over the same pair of conductors (and hence through the same pair of pins or contacts).
The differences in the signal propagation path of single-ended versus differential pair applications cause differences in the signal characteristics. Signal characteristics may include impedance, propagation delay, noise, skew, and the like. The signal characteristics are also affected by the circuitry used to transmit and receive the signals. The circuitry involved in transmitting and receiving signals differs entirely for single-ended and differential applications. The differences in the transmission and reception circuitry and the signal propagation paths yield different electrical characteristics, such as impedance, propagation delay, skew and noise. The signal characteristics are improved or deteriorated by varying the structure and configuration of the connector assembly. The structure and configuration for connector assemblies optimized for single-ended applications differ from connector assemblies optimized for use in differential pair applications.
Heretofore, it has been deemed preferable to offer a common connector assembly useful in both single-ended and differential pair application. Consequently, the connector assembly is not optimized for either applications. A need remains for a connector assembly optimized for differential pair applications.
Moreover, most connector assemblies must meet specific space constraints depending upon the type of application in which the connector assembly is used while maintaining high signal performance. By way of example only, certain computer specifications, such as for the Compact PCI specification, define the dimensions for an envelope, in which the connector assembly must fit, namely an HM-type connector which represents an industry standard connector. However, the HM connector does not necessarily offer adequate signal performance characteristics desirable in all applications. Instead, in certain applications, higher signal characteristics may be preferable, such as offered by the HS3 connector offered by Tyco Electronics Corp. It may also be preferable to use connectors suitable for frequencies higher than supported by HS3 connectors. However, certain conventional connectors that offer higher signal characteristics may not satisfy the envelope dimensions of certain connector standards.
The connector of the '391 patent provides ground shielding about each individual signal pin. One-to-one correspondence between each ground shield and each signal pin necessitates that the signal pins be spaced apart by a rather large distance. The distance between signal pins must be sufficient to accommodate an associated ground shield and retain adequate header body material to avoid compromising the integrity of the connector housing.
Further, each and every signal pin in the '391 patent is evenly spaced from all adjacent signal pins. Consequently, each signal pin is equally likely to become electro-magnetically (EM) coupled to any of the surrounding signal pins. To avoid EM coupling, the ground shields in the '391 patent are structured to attempt to isolate each signal pin. The ground shields do not achieve total isolation between certain signal pins (e.g. diagonally). To the extent that the signal pins are not isolated by the ground shields, the signal pins are spaced far from one another to further reduce EM coupling. This spacing undesirably expands the overall size of the connector assembly.
A need remains for a connector assembly for differential pair applications capable of satisfying small envelope dimensions, while affording high quality signal performance characteristics.